Objective: 1) To explain on a physiological basis the high incidence (30-50%) of low values of oxygen uptake at one minute of treadmill grade walking (VO2-1) in patients determined by coronary cineangiography to have coronary artery disease. Work to date by us has suggested that this phenomenon is related to impaired cardiac output (CO) and appears to be associated with elevated left ventricular end diastolic pressure. We will use the method of unsteady state VO2 estimation employing simple timed collection of expired air (12-15 secs) with O2 and CO2 analysis together with the CO2-N2 rebreathing technique for determination of mixed venous oxygen tension (PVO2) in normal subjects. A comparison of steady and unsteady state PVO2 values at similar values of VO2 will be made to test the hypothesis that desaturation of venous blood occurs more regularly when a given value of VO2 must be achieved at one as opposed to five minutes. The effect of cardiac disease on lowering CO will be simulated in normal subjects with propranolol to see if the concept of critical oxygen tension applies. We think that this may be the case from preliminary studies. 2) a) To enlarge the clinical correlation of the VO2-1 test by correlations with ejection fraction and response to vein grafting. To demonstrate freedom of VO2-1 as a test score from changes in physical fitness, provided subject can do the test. To explore effect of pulmonary disease, peripheral vascular disease and anemia on VO2-1 or related test b) To develop supplementary test at higher work load for subjects with CAD and normal standard VO2-1 tests. To develop a related test where VO2 at one and at two minutes is plotted against power requirement with aim of establishing that there is, in some cases of heart disease, a maximum VO2-1 lower than VO2 max of the subject whereas preliminary data suggests that VO2 max and VO2-1 max are the same in normal subjects.